Root Industries Air Wheels are available in either 110mm or 120mm. Scooter wheels come in a variety of sizes, ranging from 100mm to 125mm. The larger the wheel, the faster it is. 100mm wheels are typically entry level wheels while 125mm are geared towards the pros who need speed for big air tricks. Air Wheels are compatible with forks and decks that fit 110120mm wheels. Scooter wheels not only come in a variety of sizes but also hardness. 86a polyurethane hardness, or durometer, indicates a softer wheel that will provide more grip than an 88a durometer wheel, which has a harder polyurethane that lends to durability and speed. Softer scooter wheels are typically better for park riding, while harder wheels are geared more towards street riding.